MARSHALL: ADDITIONS TO "BRITISH CONCHOLOGY. 121 



Var. fabalis Turt. — Longer proportionately from apex to base, 

 and not so obliquely oval as the type. Jeffreys believed this to be the 

 young male of the type, forgetting that in that case they should be 

 found everywhere together, whereas it is not so. It is not the young 

 of either male or female, both sexes being represented in this variety, 

 which lives low down the littoral zone at Guernsey, where it is not 

 uncommon in small seaweeds, whereas the type and intermediate 

 forms live higher up on Fucus serratus, etc. A common form in some 

 parts of Torbay and at Guernsey is intermediate in size between this 

 and the type ; but it is shaped like the latter, lives with it, and breeds 

 with it. It is a problem why two such forms should live together 

 under identical conditions and yet keep their distinctive sizes, one 

 being just half the size of the other. 



Var. compacta Jeffr. — Sutherlandshire (Baillie) ! 



Var. aestuarii Jeffr. — The spire of this variety is more raised 

 than in any other, and in shape it is more like L. rudis ; one cannot 

 look at this curious form without a suggestive thought that it may be 

 a hybrid of Z. rudis and L. obtusata. Fossil in the Belfast deposit 

 (Praeger)! twice as large as recent specimens. 



Monstrosities are occasionally found, especially on rocky and 

 exposed shores. One is often met with having the body-whorl out of 

 the line of axis of the spire, in consequence of the animal commencing 

 a periodical growth at a lower level. A curious form from Guernsey 

 and the west of Ireland is shaped like Lacuna pallidula, being laterally 

 expanded. 



The L. palliata of Say is unlike any of our British forms, but 

 appears to me no more than a variety of Z. obtusata. The thinner 

 outer lip and pointed apex are the only permanent characters I can 

 detect in several hundred specimens from various places. With the 

 mouth towards the observer, it has the expanded aperture and thin 

 lip characteristic of Z. rudis var. pa tula ; with the mouth away, it looks 

 like Z. obtusata. Though the prominence of the spire is as variable 

 as in Z. obtusata, the apex is never flattened. In a half-grown state 

 it may be taken for Z. rudis var. ornata, as it is then rounder, with a 

 pointed apex. 



L. rudis var. saxatilis Johnst. — Shape and sculpture almost as 

 variable as in the type. Besides its own true form of a smooth, small, 

 round shell, it embraces a conglomeration of dwarfs of other varieties, 

 such zsjugosa, sulcata, patu/a, &c, all of which live huddled together 

 at high-water mark. 



Var. sulcata Leach. — Torbay ; Tenby. The prevailing character 

 of this variety is coarse and flattened ribs ; it is otherwise variable in 



